A downhole tool oftentimes includes a localized power source (e.g., a battery) for providing power to the downhole tool when the downhole tool is in a wellbore. One commonly used battery is a lithium battery; however, lithium batteries tend to overheat at temperatures greater than or equal to about 200° C. Atomic batteries may also be used downhole; however, atomic batteries do not function well below a predetermined temperature (i.e., they work best at very high temperatures).
Rather than using batteries downhole, some downhole tools generate power downhole. For example, the downhole tool may include a turbine, and an operator at the surface may pump fluid downhole that causes the turbine to rotate. The downhole tool may also include a generator that generates power in response to the rotation of the turbine.